TPO blends containing multimodal elastomers

ABSTRACT

Molded articles of thermoplastic polyolefin blends having improved resistance to fluids such as petroleum fuels after being painted with flexible coatings such as polyurethane paints and the like are disclosed. These blends include a crystalline or semi-crystalline polyolefin such as polyethylene, polypropylene, or a copolymer of ethylene and a C 3  to C 10  olefin, and a multimodal elastomer of sequentially polymerized ethylene-α-olefin monomers. The substantially crystalline polyolefin is present in an amount of 30 to 98 weight percent, while the multimodal elastomer, which is substantially amorphous, is present in an amount of about 2 to 70 weight percent. The blends may contain additional polymeric components, fillers and the like. In addition to increased paint adherence, higher weld line strength, low temperature ductility, and processability can be achieved.

This is a division, of application Ser. No. 08/747,124, filed Nov. 8,1996.

TECHNICAL FIELD

The present invention relates to thermoplastic polyolefin (“TPO”) blendswhich include a crystalline or semi-crystalline polyolefin and amultimodal elastomer, preferably of a sequentially polymerizedethylene-α-olefin copolymer which has a multimodal distribution of atleast one of molecular weight, density or α-olefin comonomers.

BACKGROUND ART

Various TPO blends are molded into lightweight, durable articles whichare useful as automobile parts, equipment housings, toys and the like.Often, it is desired to paint such components for aesthetic orfunctional purposes. When these blends contain combinations ofcrystalline or semi-crystalline polymers and elastomers, however, thesurface of the molded article generally must be treated so that thepaint can durably adhere to the article. Paint adhesion is a particularconcern in articles molded from TPO blends such as those described inU.S. Pat. Nos. 4,480,065, 4,439,573 and 4,412,016.

One way to obtain good paint adhesion is to treat the surface of thearticle with an interlayer coating to promote or enhance adhesion. Whenthe article is to be used in environments which include high humidityconditions, or is to be exposed to petroleum fuels or solvents, however,the interlayer coatings can be detrimentally affected with reduced paintadhesion as a result. Thus, the paints will chip or peel away during useof the article. An example of this is the use of a painted molded TPOautomobile bumper. Such articles will not be approved for use onautomobiles unless the paint retains suitable adhesion properties in thepresence of such fluids and moisture.

U.S. Pat. No. 5,498,671 discloses a solution to this problem byutilizing a combination of low and high molecular weightethylene/propylene/diene monomer (EPDM) rubbers with crystalline orsemi-crystalline polyolefins. The resultant TPO blends possess excellentadhesion to paints, with superior resistance to petroleum fluids andmoisture. A minor drawback of this system is the use of the lowmolecular weight EPDM, which is a sticky, viscous liquid at roomtemperature. Thus, it is necessary to carefully handle this viscousfluid, such as by retaining it in plastic bags, or pumping toefficiently facilitate its introduction into an external mixer whichmixes the components together. It would be desirable to retain the goodpaint adherence of such materials, however, while improving the ease ofhandling of the components during manufacture of the blend.

SUMMARY OF THE INVENTION

The present invention relates to a thermoplastic polyolefin blend whichincludes a polyolefin component of a substantially crystalline polymerin an amount of about 30 to 98 percent by weight of the blend; and anelastomer of a sequentially polymerized ethylene α-olefin copolymerhaving a multimodal distribution of at least one of molecular weight,density or α-olefin monomers, and being present in an amount of about 2to 70 percent by weight of the blend.

The polyolefin is preferably present in an amount of about 40 to 96 andmost preferably 50 to 95 percent by weight of the blend, and is acrystalline or semi-crystalline polyethylene polymer, polypropylenepolymer, or copolymer of ethylene and a C₃ to C₁₀ α-olefin. Themultimodal elastomer has an overall Mw/Mn ratio of at least 3, issubstantially amorphous, and is preferably present in an amount of about4 to 60 and more preferably about 5 to 50 percent by weight.Advantageously, a bimodal elastomer is used with the different modesbeing present in a split of between about 75:25 and 25:75.

In one embodiment, at least two modes are present, having weight averagemolecular weight modes which differ by at least about 25,000 andpreferably by about 50,000, 100,000 or more, with the higher molecularweight of the higher molecular weight mode being no greater than about350,000. One mode may advantageously have a molecular weight which is amultiple of at least about 1.5 and preferably 5 and 50 times higher thanthat of the other mode.

In an embodiment, termed a “high-low” split, one mode has a lowermolecular weight of about 30,000 or less and the other mode has a highermolecular weight of at least about 150,000 to provide a non-liquidpolymer that can be handled as a solid at room temperature. In anotherembodiment, called the “high-high” split, one mode has a molecularweight of at least about 50,000 and the other has a molecular weight ofat least about 100,000. In the “high-high” split, it is advantageous forone of the molecular weights to be about 75,000 and the other molecularweight to be at least about 150,000.

In another embodiment of the invention, at least two modes havingdensities which differ by at least about 0.005 grams per cubiccentimeter (g/cc) are used. Preferably, one mode has a density ofgreater than 0.85 g/cc and the other mode has a density of less thanabout 0.96 g/cc, with the difference between densities of the modesbeing less than about 0.1, preferably less than about 0.05 and morepreferably less than 0.03 g/cc.

In yet another embodiment of the invention, at least two modescontaining comonomers which differ in length by at least one carbon atomare used. Preferably, the comonomers of the modes differ in length by atleast two carbon atoms, and one of which is propene, butene, hexene oroctene.

The blends of the invention may also include at least one additionalpolymeric component in an amount of between about 1 and 20 percent byweight of total blend. At least two different additional polymericcomponents may be present, but in a total amount of about 3 and 35percent by weight of the blend. One suitable polymeric component is acopolymer of ethylene and a C₃ to C₁₀ (three to ten carbon atoms)α-olefin or a terpolymer of that copolymer and a diene monomer. Anothersuitable polymeric component is a copolymer of ethylene and an α-olefinwhich is made with a Kaminsky or metallocene catalyst.

If desired, the blend may include a filler in an amount of about 1 to 30percent by weight of the blend. Preferred fillers such as talc, mica,glass, or calcium carbonate can be used. Other conventional additivessuch as nucleating agents, oils and the like can be included if desired.

The blends can be formed into molded articles having one or more outersurfaces, with at least one of the outer surfaces including a coatingthereon for aesthetic or functional purposes, if desired. Although anycoating can be used, a two component polyurethane material coating ispreferred.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a graphical illustration of molecular weight distribution(MWD) of a useful bimodal elastomer which represents one embodiment ofthe TPO blends of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The polyolefin component of the TPO blends of this invention is acrystalline or semi-crystalline polyethylene or polypropylene polymer orcopolymer, or a copolymer of ethylene and a C₃ to C₁₀ alpha-olefin. Thecopolymer may be a random copolymer, a block copolymer or a graftcopolymer.

The crystallinity of this component can range from mostly crystalline(above 50%) to fully crystalline (i.e., 100%), i.e., that of a highlycrystalline material, or by a degree of crystallinity sufficient toexhibit partially crystalline or semi-crystalline behavior, i.e., 30% to70% crystallinity. When polypropylene is used as this component, it hasabout 30 to 98%, and preferably about 50 to 80%, crystallinity asmeasured by X-ray analysis or solvent extraction. The term“substantially crystalline” is used herein to designate those polymersor copolymers which are crystalline or semi-crystalline.

The polyolefin component may be utilized in an amount of between about30 and 98 percent by weight of the blend, preferably at between about 40and 96 percent and most preferably at between about 50 and 95 percent.When mixtures of substantially crystalline polyolefin polymers orcopolymers are used, the total amount will be within these rangesalthough the individual amounts of each can vary as desired.

The elastomer component is a substantially amorphous copolymer ofethylene and at least one α-olefin having between 3 and 18 carbon atoms.“Substantially amorphous” means that the copolymer has less than 20%percent by weight of crystallinity. Although any 3 to 18 carbon α-olefincan be used, propene, butene, hexane and particularly octene arepreferred. This elastomer component is present in an amount of about 2to 70, preferably about 4 to 60 and most preferably about 5 to 50percent by weight of the blend. If desired, an addition monomer such asa diene may be added.

This elastomer component has a multimodal distribution of at least oneof molecular weight, density or α-olefin monomers. There is notheoretical limit to the number of modes that could be present in thiscomponent, although a finite number of 10 modes or less would be usedfor most applications. For purposes of illustrating preferredembodiments of the invention, a bimodal distribution will be shown. Oneof ordinary skill in the art would be well aware of how to produce anydesired number of modes in the elastomer by varying the relative amountsof proportions of each mode, and the invention should not be limited tobimodal elastomers for that reason.

When a bimodal distribution of different molecular weight elastomers isprovided, a MWD of the elastomer would be of the type illustrated inFIG. 1. One experimental product having this distribution is availablefrom The Dow Chemical Company, and is known as CO1R02. As shown in FIG.1, this product includes one mode which has a weight average molecularweight of about 250,000, and another mode which has a weight averagemolecular weight of about 15,000.

The multimodal elastomers of the invention are formed in situ byinterpolymerization using multiple reactors or reactors systems and aconstrained geometry catalyst system, or a single reactor havingmultiple stages. Two reactors are conveniently used, although multiplereactors (i.e., more than 2) in any kind of series or parallelconfiguration can be used. Suitable multiple reactor configurationsinclude a loop reactor, spherical reactor, stirred tank reactor,plug-flow tube reactor, or reaction extruder.

If desired, different catalyst can be used in each reactor. For example,a first reactor could utilize a constrained geometry catalyst, such asis described in U.S. Pat. No. 5,064,802, while a second reactor canutilize a heterogeneous Ziegler catalyst system, such as is described inU.S. Pat. No. 4,314,912. An exemplary in situ interpolymerization systemis disclosed in U.S. Pat. No. 5,844,045. The content of each of thesedocuments is expressly incorporated by reference herein to the extentnecessary for one to understand the methods of making these multimodalelastomers. The present invention relates to the use of these multimodalelastomers in a TPO blend rather than to the various methods formanufacture of such elastomers.

Any of a wide range of different properties would be useful for themultimodal elastomeric component of the present TPO blends. In a firstembodiment for a multimodal molecular weight elastomer, for example, thelowest molecular weight could be as low as about 3,000 to 7,000(typically 5,000), but generally would be about 10,000 to 20,000(typically 15,000) or more. The highest molecular weight can be as highas about 350,000 with existing technology, but generally would be aboveabout 150,000, more particularly, greater than about 160,000 to 180,000.The difference between the lowest and highest molecular weights at aminimum should at least be significant or measurable. In many cases, theone molecular weight will be at least about 1.5 times to as high asbetween 5 and 50 times the molecular weight of other. A weight averagemolecular weight difference of about 25,000 to 50,000 is generallysufficient to provide the advantages of the present elastomer componentfor most blends.

In a second embodiment, suitable multimodal elastomers include thosehaving a lowest molecular weight mode of at least 75,000, preferably85,000 and most preferably 100,000, with a highest molecular weight modeof at least 115,000, preferably 125,000 and most preferably 150,000.Highly advantageous multimodal elastomers have a lowest weight averagemolecular weight mode of more than 100,000 and a highest weight averagemolecular weight mode of above 200,000.

The overall weight average molecular weight of the elastomer would thusbe in the range of about 85,000 and 350,000 and preferably between about105,000 to 250,000. Molecular weights can be measured using the methoddescribed in U.S. Pat. No. 5,272,236, the content of which is expresslyincorporated herein by reference thereto. Another way to preparemultimodal elastomers is by providing relatively high and low densitysegments in the elastomer. This is done by providing different types orconcentrations of α-olefin monomers for sequential reaction withethylene in the manner explained previously. For example, a low densitymonomer could be used to provide an overall density of as low as about0.85 g/cc when polymerized with ethylene, while a high molecular weightcomponent can provide a density of as high as about 0.96 g/cc whenpolymerized with ethylene. Small deviations between the high and lowdensities can provide meaningful differences in the resulting bimodalelastomer. If desired, a difference of at least about 0.003 g/cc isacceptable, although values of 0.005 g/cc to as high as 0.1 g/cc can beused. The overall density of the elastomer can vary, but preferablywould be less than about 0.95, preferably less than about 0.9 and morepreferably less than about 0.87 g/cc.

The relative split of high and low components in the elastomer can varyover wide ranges. When two different modes are used, relative amounts of5:95 to 95:5 provide measurable differences in high and low density ormolecular weight values. When greater than 95 parts of one component isused, the effect of the other component becomes relativelyinsignificant. In addition, the use of a high amount of one componentcompared to the other is an inefficient use of the second reactor due tothe relatively small amounts of the second component that are to bereacted. Thus, it is typical to use relative amounts of between 75:25and 25:75 for bimodal elastomers. For certain embodiments, relativeamounts of between 2:1 and 1:1 are conveniently formulated and provideadvantageous bimodal properties. Thus, a preferred range of about 70:30and 30:70 is used. When other multimode distributions are desired, therelative amounts of each mode is varied appropriately. For five modes,for example, each component can vary between 10 and 35 parts, providedthat the overall ratio totals 100. As a specific example, a ratio of10:15:20:20:35 is possible, but a wide range of other proportions couldbe used if desired.

It is also possible to utilize different α-olefin monomers to achievemultimodal properties. When this is done, the α-olefin monomers candiffer by one carbon atom and preferably by 2, 3 or more carbon atoms.Particularly advantageous bimodal elastomers can be made with propeneand octene, although other combinations may be used.

One way to make such elastomers is to add each monomer in a separatereactor. For a bimodal elastomer, one monomer is added in the firstreactor and the second monomer in another reactor. When this is done,the relative splits mentioned above can be used to define the relevantamounts of each monomer. Also, a mixture of the monomers can be added toeach reactor, with a greater amount of one monomer provided in themixture which is directed to the first reactor, and a greater amount ofthe other monomer provided in the mixture which is directed to thesecond reactor. Advantageously, about 2:1 to 4:1 of the monomers in thefeed to the first reactor and about 1:2 to 1:4 of the monomers in thefeed for the second reactor is used. Other ratios can be used whengreater numbers of monomers are used.

As noted above, the amount of the multimodal elastomer to beincorporated in the TPO blends of the present invention can vary fromabout 2 to 70 percent by weight of the blend. When the final blendincludes only the polyolefin component and the multimodal elastomer,relative amounts of about 4:6 to 5:1 (i.e., 40:60 to 80:20) wouldtypically be used. The polyolefin is generally present in equal orgreater amounts compared to the elastomer. Lesser amounts of themultimodal elastomer, i.e., less than about 35 to 50 percent by weight,would be used where other polymer additives are included in the blend.

The addition of the multimodal elastomer provides blends which exhibitsuperior performance after molding and painting with typical flexibleautomotive or other coatings. In particular, increased resistance togasoline or other is petroleum fuels has been observed. Before painting,the molded TPO blend surfaces are pretreated with a conventionalpowerwash, and a coating of a conventional chlorinated polyolefinadhesion promoter is used for greatest paint adhesion. Paints of alltypes can be used, including one pack or two component polyurethanecoatings, which are then baked at temperatures around 80° C.

When superior coated performance after painting molded TPO blends isrequired, it is advantageous to include a multimodal elastomer having ahigh/low molecular weight distribution. Thus, the high weight averagemolecular weight component would be from at least about 150,000 to about175,000, while the low weight average molecular weight component wouldbe from less than about 15,000 to 35,000. Preferably, the lowermolecular weight mode would have a density of less than 0.88, morepreferably less than 0.875 and most preferably less than 0.87 g/cc. Thisproduct preferably has, a weight average molecular weight/number averagemolecular weight (Mw/Mn) ratio of at least 3, preferably greater than 6,more preferably greater than 8 and most preferably greater than 10 witha melt flow index @ 10 Kg and 2 Kg at 190° C. (I10/I2) that is greaterthan 7 and preferably greater than 10. The Mw/Mn ratio should be greaterthan the difference of (I10/I2)—6.63, more preferably (I10/I2)—5.63 andmost preferably (I10/I2)—4.63 for optimum enhanced paintability. Also,the split of high and low molecular weight material would be between75:25 and 25:75 and preferably about 50:50.

For additional advantages with regard to weld-line strength,low-temperature impact toughness and improved injection moldingprocessability, it is preferable to use a multimodal elastomer having ahigh/high molecular weight distribution. In this embodiment, onemolecular weight is at least about 50,000, while the other is at leastabout 75,000. Preferably, one molecular weight is at least about100,000, while the other is at least about 150,000 to 200,000.

The examples illustrate the most preferred TPO blends of this invention.Also, all molecular weights are presented in weight average molecularweight unless otherwise indicated.

A wide variety of additional polymeric components may be added to theTPO blends of the present invention, if desired. One additionalpolymeric component is a substantially amorphous copolymer of ethylenewith a C₃-C₁₀ α-olefin or a terpolymer of the ethylene-α-olefin and adiene compound. At least two of these additional components can be used,if desired, each having a different molecular weight. Such polymericcomponents would have a molecular weight distribution Mw/Mn of less thanabout 5. Also, a substantially amorphous copolymer of ethylene and anα-olefin, preferably propene, butene, hexene or octene, polymerizedusing Kaminsky or metallocene catalysts and having a relatively narrowmolecular weight distribution of less than about 1.8, can be used.

These additional polymeric components can each be added individually inan amount of about 1 to 20 percent by weight. When two or more areadded, the total amount of these additional components will generally bebetween 3 to 35 percent by weight.

When desired, fillers can be added to the present TPO blends. Preferredfillers include inorganic materials such as talc, mica, glass, calciumcarbonate or the like. The amount of filler will generally be in therange of about 2 to 30 and preferably about 3 to 15 percent by weight ofthe blend.

The TPO blends of the invention have excellent paintability, a broadrange of stiffness values, as well as high impact and tensile strengthswhich make them suitable for automotive applications.

Certain blends also exhibit superior weld line strength, low temperaturetoughness and improved processability during injection molding. The TPOblends of the invention can be molded or otherwise formed or shaped toproduce articles that are lightweight, durable, and have surfaces thatare paint receptive. The articles can be treated with an adhesionpromoter and then painted, and the paint cured at temperatures exceeding80° C. to produce a durable and attractive finish. Any of theconventional adhesion promoters can be used with good results.

The polymer blends of the invention can be coated with paints,particularly with paints such as commercially available two-componentpolyurethanes, to provide products with superior fluid and petroleumresistance. The blends of the invention also may be coated with paintswhich have active functional groups such as acrylics, polyesters, epoxyresins, carbodiimides, urea resins, melamine-formaldehyde resins,enamines, keto-imines, amines, and isocyanates to provide products withimproved fluid resistance. These types of paints are. well known in thepaint and coatings industry.

Various additives can be incorporated into the polymer blends of theinvention to vary the physical properties of the blends of the inventionwhile retaining good paint adhesion. These additives may includepigments, dyes, processing aids, anti-static additives, surfactants andstabilizers such as those which generally are used in polymericcompositions. Other conventional additives, such as nucleating agents,oils, lubricants, antioxidants, UV stabilizers, fungicides,bacteriocides and the like, can be included as desired. Particularlyuseful additives may include styrene-maleic anhydride copolymers andcationic surfactants for improving moisture resistance, and well knowncopolymers such as ethylene-acrylic acid copolymers (“EAA”) andethylene-methacrylic acid copolymers (“EMAA”), or mixtures or blendsthereof.

The fluid resistance of preforms of the polymer blends of the inventionbearing a single coating of 2-part commercially available polyurethaneis evaluated by placing the coated preforms into a gasoline bath. Thegasoline bath may be mixtures of any of 90% unleaded gasoline and 10%ethanol; 90% unleaded gasoline and 10% methanol; or 100% unleadedgasoline. The preforms employed are 2½″ squares, or possibly 1″×3″ bars.The coated preform remains immersed in the gasoline bath until failure,that is, paint at the edges of the preform curls away from the preform.The coated preform then is removed from the bath and the time to failurerecorded. The fluid resistance of the coated preforms are shown in theexamples.

The % peel area of the paint from the preform also is a measure of theability of the preform to retain paint against the action of petroleumfluids such as gasoline. The painted preform is removed from thegasoline bath after a 30-minute immersion and the area, if any, that isfree of paint is measured. The % peel area is determined by dividing thearea of the preform free of paint by the original painted area of thepreform. Low % peel area is desired.

EXAMPLES

The invention will now be described by reference to the followingnon-limiting examples.

The blends of the Examples are formed by mixing the components in theamounts recited. Blending of the components is performed by well knownmethods and devices such as Banbury mixers and extrusion equipment. Thepolymer blends can be molded into shaped preforms by known methods suchas extrusion, injection molding, blow molding, or thermoforming. Theshaped preforms of the polymer blends are coated with a single layer ofpaint of two-part polyurethanes in accordance with well known methodssuch as spraying. The polymer blends also can be pelletized for storageand shipment prior to molding into shaped articles.

Generally, processing of the polymer blends of the invention can beperformed using Banbury mixers or twin screw extruders. When a Banburymixer is employed to prepare these blends, a single screw extruder canbe used to pelletize that component blend. The resulting pellets thenare supplied to an injection molding machine for manufacture of moldedarticles.

During preparation of these blends with a Banbury mixer, the rampressure in the Banbury mixer is about 30-35 psi. Mixing is continueduntil fluxing temperature is achieved, i.e., the temperature at whichthe viscosity of the blend drops sharply. When fluxing temperature isachieved, mixing is terminated and the resulting batch of material isremoved from the Banbury mixer. The batch then is ground into chipsand/or pelletized in a single screw extruder.

Pellets of the formed component blends are supplied to an injectionmolding machine for injection molding into shaped products. Processingconditions are shown below in Table 1.

TABLE 1 Processing Conditions BANBURY MIXING ROTOR SPEED (RPM) 185 RAMPRESSURE (PSI)  32 TIME TO FLUX (SEC)  95 FLUX TEMP (° F.) 360 BATCHTEMP (° F.) 410 PELLETIZING SINGLE SCREW EXTRUDER END ZONES TEMP (° F.)360 CENTRAL ZONE TEMP (° F.) 380 SCREW SPEED (RPM)  95 MELT TEMP (° F.)375 MOLDING TEMPERATURES END ZONE 1 340 CENTRAL ZONE 2 360 CENTRAL ZONE3 360 END ZONE 4 340 SCREW SPEED (RPM)  90 MOLD TEMP (° F.)  80INJECTION TIME (SEC)  10 COOLING TIME (SEC)  25 INJECTION PRESSURE (PSI)550 FILLING TIME (PSI)  10 HOLDING PRESSURE (PSI) 430 HOLDING TIME (SEC) 15 BACK PRESSURE (PSI)  50

The bimodal elastomers are made as described above, with informationprovided in the Examples as to the precise formulation of suchmaterials.

Examples 1-8

Useful TPO blends along with properties such as gasoline resistance meltflow rate and density, are shown in Table 2. In these examples, thesurfaces of the articles to be painted are conventionally powerwashedand treated with a conventional chlorinated polyolefin adhesionpromoter. A two component polyurethane coating is then applied and curedby baking at about 80° C.

TABLE 2 Material Type Form Kind C-1 C-2 C-3 C-4 Ex 1 Ex 2 C-5 C-6 Ex 3Ex 4 Ex 5 Ex 6 Ex 7 Ex 8 20mfr PP Flake 65 65 65 65 65 65 65 65 65 65 6565 65 65 EPDM I Bale 14 14 14 14 14 14 15.6 21.3 20.7 19.1 19.1 EO 1Pellets 21 14 15.4 EO 2 Pellets 35 21 T-56-DCPD Liquid EPDM 7 300-1Pellets EOBM 21 19.4 CO1R02 Pellets EOBM 21 13.7 CO1R02A Pellets EOBM 21CO1R03 Pellets EOBM 14.3 CO1R04 Pellets EOBM 15.9 CO1R05 Pellets EOBM15.9 C18R3 Pellets EOBM 35 19.6 B225 Pellets AO 0.3 0.3 0.3 0.3 0.3 0.30.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Property Units E-10 w. min 10 26 1020 >120 >120 >120 21 >120 >120 >120 >120 >60 41 WB130CDI/ R784/R788 MFR,dg/min. 9.4 9.4 10.2 16.2 13.9 13.3 13.7 14.5 14.1 14.2 12.1 13.9 17.115.3 230° C./ 2.16 Kg Notes: 20mfr PP Polypropylene, Melt Flow Rate = 20dg/min @ 230° C./2.61 Kg EPDM I 4% Ethylidene norbornene, C2/C3 = 58/42,Mooney = 35 ML (1 + 4) @ 100° C. EO 1 Ethylene-Octene Copolymer, 1.0 MI@ 190° C./2.61 Kg; Mw/Mn = 2.0, I10/I2 = 8.1 EO 2 Ethylene-OcteneCopolymer, 0.5 MI @ 190° C./2.61 Kg; Mw/Mn = 2.1, I10/I2 = 7.3 T-56-DCPDEPDM 9.5% Dicyclopentadiene, C2/C3 = 48/52, Mv = 5,500 300-1 −36 wt % of4K Mw 0.886 g/cc, −64 wt % of 158K Mw 0.862 g/cc, Overall Mw = 102K,0.868 g/cc; Mw/Mn = 23 CO1R02 −51 wt % of 12.7K Mw 0.87 g/cc, −49 wt %of 227K Mw 0.857 g/cc, Overall Mw = 118K, 0.863 g/cc; Mw/Mn = 11 CO1R02A−56 wt % of 14.5K Mw 0.87 g/cc, −44 wt % of 247K Mw 0.858 g/cc, OverallMw = 116K, 0.864 g/cc; Mw/Mn = 11 CO1R03 −50 wt % of 9K Mw 0.877 g/cc,−50 wt % of 215K Mw 0.861 g/cc, Overall Mw = 111K, 0.867 g/cc; Mw/Mn =14, I10/I2 = 17 CO1R04 −44 wt % of 7.1K Mw, 0.877 g/cc, −56 wt % of 217KMw, 0.865 g/cc, Overall Mw = 125K, 0.871 g/cc; Mw/Mn = 21, I10/I2 = 12C01R05 −44 wt % of 5.7K Mw, 0.874 g/cc, −56 wt % of 214K Mw, 0.865 g/cc,Overall Mw = 122K, 0.87 g/cc; Mw/Mn = 21, I10/I2 = 14

As can be seen from the comparison of Controls 1-4 with Examples 1-2,the use of a bimodal elastomer according to the invention provideshigher melt flow rates of the TPO blend, as well as significantlyincreased gasoline resistance of up to 5 times that of the comparativeexamples for painted molded articles of such blends.

Control 4 shows that the low molecular weight mode must have a densityless than 0.88 g/cc to achieve good paint adhesion.

A comparison of Control 5 with Examples 1 through 6 illustrates thatexcellent paint adhesion can be obtained without having to use a liquid,low molecular weight EPDM.

Examples 3-6 illustrate the effect on melt viscosity by varying therelative amounts of high molecular weight EPDM and bimodal elastomer.These examples also show that the use of different molecular weightdistributions in the bimodal elastomer within the ranges shown does notsignificantly affect the performance of the blend of its advantageouspaint adherence properties.

Examples 9-10

These examples illustrate the comparative properties and performance ofTPO blends containing a high/high bimodal elastomer with differentconventional formulations containing poly(ethylene α-butene orco-octene) elastomers. The formulations and properties are shown inTable 3.

A comparison of Control 7 and Example 9 shows that the use of thebimodal elastomer provides much better weld line strength than the useof the poly(ethylene-octene) elastomer.

Example 10 compared to Controls 8-11 shows that the use of the bimodalelastomer provides much better weld line strengths and low temperatureimpact properties compared to blends containing poly-(ethylene-butene or-octene) elastomers. In addition, the gloss for the painted article ofExample 10, which included the bimodal elastomer, was significantlyimproved over that of Control 8, which included a mixture ofpoly-(ethylene -butene and -octene) elastomers.

TABLE 3 Material Type C-7 Ex 9 C-8 C-9 C-10 C-11 Ex 10 20 MFR PP 60 6035 MFR HIPP 62 62 62 62 62 EBR 22 EOR1 11 EOR2 40 33 23 EOR3 33 10Bimodal EOR 40 33 Filler 5 5 5 5 5 Property Izod @ RT (ft-lbs/in) PB NBNB NB NB Izod @ −10C {ft-lbs/in) 1.26 PB 3.09 PB PB Izod @ −30C (9ft-lbs/in) 1.44 1.43 1.49 1.68 2.39 WL Flex Peak Stress (psi) 2854 31693567 3919 3413 3774 4253 WL Flex En. to Break (in-lb) 2.85 3.01 0.741.08 0.67 0.89 3.03 WL Tensile Break Stress (psi) 1930 2042 2349 20191855 2059 2567 WL Tensile Break Elong. (%) 8 11.1 3.2 2.7 2.4 2.8 4.3 WLTensile En. to Break (in-lb) 15.4 22.9 6.3 4.4 3.6 4.7 10.2 Gloss 68.862.6 Notes 20 MFR PP Polypropylene, Melt Flow Rate = 20 dg/min @ 230°C./2.16 Kg 35 MFR HIPP Polypropylene, Melt Flow Rate = 35 dg/min @ 230°C./2.16 Kg EBR Poly(ethylene-co-butene); C2 = 80%, MFR @ 190° C., 2.16Kg = 0.8 dg/min EOR1 Poly(ethylene-co-octene); C2 = 80%, MFR @ 190° C.,2.16 Kg = 5 dg/min EOR2 Poly(ethylene-co-octene); C2 = 80%, MFR @ 190°C., 2.16 Kg = 1 dg/min EOR3 Poly(ethylene-co-octene); C2 = 80%, MFR @190° C., 2.16 Kg = 0.5 dg/min Bimodal EOR Bimodalpoly(ethylene-co-octene); high mode MW = 260,000; low mode MW = 114,000Izod Test NB = no break; PB = partial break; WL = weld line

Upon reviewing the data, it is seen that, in the first embodiment, thebest results are obtained when a multimodal elastomer having high andlow molecular weight components present, provides enhanced paint bondingto the molded polymer blend. In the second embodiment, better physicalproperties, in particular weld line strength and low temp impactstrength, are attained compared to blends that do not contain multimodalelastomers.

Other aspects of the invention will be apparent to those skilled in theart from consideration of the specification, or from practice of theinvention disclosed herein. For example, despite the preferredembodiment of the present invention which includes a bimodal elastomer,one of ordinary skill in the art would realize that multimodalelastomers with three, four, five or even more modes can be provided bymaking the elastomer in multiple, sequentially arranged reactors inaccordance with the principles disclosed herein for two reactors. Suchmultimodal elastomers are considered as part of the present invention,since they would contain at least two modes as specifically disclosedherein. Thus, it is intended that the specification and examples beconsidered as exemplary only, with the scope and spirit of the inventionbeing indicated by the following claims.

What is claimed is:
 1. A molded article comprising a thermoplasticpolyolefin blend of: a polyolefin component of a substantiallycrystalline polymer in an amount of about 30 to 98 percent by weight ofthe blend; and an elastomer of a sequentially polymerizedethylene-α-olefin copolymer having a multimodal distribution comprisingfirst and second modes of at least one of: (A) molecular weight, withthe first and second modes differing by at least about 25,000 in weightaverage molecular weight, with the molecular weight of the highermolecular weight mode being no greater than about 350,000; (B) density,with the first and second modes differing by at least about 0.005 g/cc;or (C) α-olefin monomers, with the first and second modes includingcomonomers which differ in length by at least one carbon atom; whereinthe multimodal distribution has between 2 and 10 modes, the elastomerhas an overall density of 0.9 or less and an overall Mw/Mn ratio whichis at least 3 and greater than (I₁₀/I₂—4.63), and the elastomer ispresent in an amount of about 2 to 70 percent by weight of the blend. 2.The article of claim 1 wherein the polyolefin component is present inthe blend in an amount of about 50 to 95 percent by weight of the blend,has a crystallinity of above 50%, and is a polyethylene polymer,polypropylene polymer, or copolymer of ethylene and at least one of a C₃to C₁₀ α-olefin.
 3. The article of claim 1 wherein the multimodalelastomer is amorphous and is present in an amount of about 4 to 60percent by weight.
 4. The article of claim 1 wherein the first andsecond modes of the multimodal elastomer have weight average molecularweights which differ by at least about 50,000.
 5. The article of claim 4wherein one mode has a weight average molecular weight which is amultiple of from at least 1.5 to about 50 times that of the other mode.6. The article of claim 5 wherein the molecular weight of one mode isabout 30,000 or less and the molecular weight of the other mode is atleast about 150,000.
 7. The article of claim 6 wherein the lowermolecular weight mode has a density of less than about 0.88 g/cc, aslong as the overall density does not exceed 0.9.
 8. The article of claim4 wherein the molecular weight of one mode is about 100,000 and themolecular weight of the other mode is at least about 200,000.
 9. Thearticle of claim 3 wherein the molecular weight of one mode is at leastabout 75,000 and the molecular weight of the other mode is at leastabout 115,000.
 10. The article of claim 3 wherein the first and secondhas modes of the multimodal elastomer have densities which differ by atleast about 0.005 g/cc.
 11. The article of claim 10 wherein themultimodal elastomer has one mode of a density of at least 0.85 g/cc andthe other mode of a density of less than about 0.96 g/cc, with thedifference between the highest and lowest mode densities being less thanabout 0.1 g/cc, as long as the overall density does not exceed 0.9. 12.The article of claim 1 wherein the first and second modes of themultimodal elastomer include comonomers which differ in length by atleast one carbon atom.
 13. The article of claim 1 wherein the first andsecond modes of the multimodal elastomer have comonomers which differ inlength by at least two carbon atoms, and one of which is propene,butene, hexene or octene.
 14. The article of claim 1 further comprisingat least one additional polymeric component in an amount of betweenabout 1 and 20 percent by weight of the blend.
 15. A molded articlecomprising a thermoplastic polyolefin blend of: a polyolefin componentof a substantially crystalline polymer in an amount of about 30 to 98percent by weight of the blend; and an elastomer of a sequentiallypolymerized ethylene-α-olefin copolymer having a multimodal distributioncomprising first and second modes of at least one of: (A) molecularweight, with the first and second modes differing by at least about25,000 in weight average molecular weight, with the molecular weight ofthe higher molecular weight mode being no greater than about 350,000;(B) density, with the first and second modes differing by at least about0.005 g/cc; or (C) α-olefin monomers, with the first and second modesincluding comonomers which differ in length by at least one carbon atom;wherein the multimodal distribution has between.2 and 10 modes, theelastomer has an overall density of 0.9 or less and an overallM_(w)/M_(n) ratio of at least 3 and greater than (I₁₀/I₂—4.63), theelastomer is present in an amount of about 2 to 70 percent by weight ofthe blend, and at least two different additional polymeric componentsare present but in a total amount of about 3 and 35 percent by weight ofthe blend.
 16. The article of claim 15 wherein one additional polymericcomponent is a copolymer of ethylene and a C₃ to C₁₀ α-olefin or aterpolymer of ethylene and a C₃ to C₁₀ α-olefin and a diene monomer, andanother additional polymeric component is a copolymer of ethylene and anα-olefin which is made with a Kaminsky or metallocene catalyst.
 17. Thearticle of claim 1 further comprising a filler in the amount of about 1to 30 percent by weight of the blend.
 18. The article of claim 17wherein the filler is talc, mica, glass, or calcium carbonate.
 19. Thearticle of claim 1 having an outer surface, an overall molecular weightof between 70,000 and 300,000, and an overall density of between 0.85and 1.25 g/cc.
 20. The article of claim 19 wherein the overall densityis between 0.85 and 0.95 g/cc.
 21. The article of claim 19 wherein atleast a portion of the outer surface includes a coating thereon.
 22. Amolded article comprising a thermoplastic polyolefin blend of: apolyolefin component of a substantially crystalline polymer in an amountof about 30 to 98 percent by weight of the blend; and an elastomer of asequentially polymerized ethylene-α-olefin copolymer having a multimodaldistribution comprising first and second modes of at least one of: (A)molecular weight, with the first and second modes differing by at leastabout 25,000 in weight average molecular weight, with the molecularweight of the higher molecular weight mode being no greater than about350,000; (B) density, with the first and second modes differing by atleast about 0.005 g/cc; or (C) α-olefin monomers, with the first andsecond modes including comonomers which differ in length by at least onecarbon atom; wherein the multimodal distribution has between 2 and 10modes, the elastomer has an overall density of 0.9 or less and anoverall M_(w)/M_(n) ratio of at least 3 and greater than (I₁₀/I₂—4.63),and the elastomer is present in an amount of about 2 to 70 percent byweight of the blend and wherein the molded article has an overallmolecular weight of 70,000 to 300,000, an overall density of 0.85 g/ccto 0.95 g/cc, and an outer surface at least a portion of which includesa coating thereon, wherein the coating comprises a two-componentpolyurethane material.
 23. The article of claim 1 wherein the multimodalelastomer has a Mw/Mn ratio that is greater than 3 with a melt flowindex @ 10 Kg and 2 Kg at 190° C. (I10/I2) that is about 7 or greater.24. The article of claim 1 wherein the multimodal elastomer has a Mw/Mnratio that is greater than 6 with a melt flow index @ 10 Kg and 2 Kg at190° C. (I10/I2) that is greater than 10.